Electronic devices comprising electronic components are housed in casings. The casings protect the electronic components from damage. Electronic components are particularly sensitive to damage from liquids, for example, caused by interaction with water (with or without impurities). With liquid, harming particles (e.g. ions) can access sensitive areas inside the electronic device and cause, for example, corrosion, electrochemical migration and/or short circuiting of the electronic device.
Electronic casings are often made from multiple (housing) parts which are joined together along sealing lines. Unless measures are taken, these sealing lines will allow the ingress of liquid into the casing, leading to damage of the electronic components contained therein. Even quite narrow channels will allow the ingress of liquid into the casing.
One key transfer method of liquids, particularly in narrow channels, is capillary attraction (often referred to as capillary action), in which liquid transfers in capillary channels driven by capillary force. These capillary channels are typically formed between different exterior parts, such as the so-called A and B casing covers of a mobile phone. However, such channels can also be formed between interior components, such as between a Printed Wiring Board (PWB) and a keypad dome sheet in a mobile phone.
The problem of liquid ingress into electronic devices is a widely recognised problem. Some solutions focus on liquid (water) resistance increase, for example, by using different kind of seals between components, or even integrating seals into the casing components. This increases material cost/manufacturing/assembling complexity. Some solutions focus on increasing moisture/liquid resistance of critical components themselves. Again, this also increases material cost.